Get Google Partner API using API Explorer to work to return some data

Basicall all I am looking for at the moment is to create a basic project in Google Cloud, Enable Google Partners API and use the API Explorer to get some data and play around with it. You can create any dummy gmail to create this test environment for me.

I get 403 permission denied when I try to do that and I can't figure out why. I want the steps to be explained in details so I know what my problem was.